This invention relates generally to devices for inserting a lance into a pressurized container, in particular a blast furnace. More particularly, this invention relates to a device for equipping an opening for the axial insertion of a lance into a pressurized container such as a blast furnace without loss of leak tightness, either during insertion of the lance or total closure of the opening when the lance is entirely withdrawn.
A device of this kind for inserting a measuring probe into a blast furnace is known from U.S. Pat. No. 3,643,508. This device comprises a closure member which is fixed with one end on a pipe of a blast furnace and which supports an axial sealing member at its free end. The closure member comprises a double disc fitted, on one side, with a solid disc and, on the other side, with a disc pierced with a through opening for the lance. This double disc is pivotable about a pivot axis parallel to the central axis of the device and is provided with a slight axial clearance along this pivot axis. In order to close the pipe of the blast furnace, the solid disc is pivoted into an axial position between a first flange, fixed onto the pipe of the blast furnace, and a second flange, supporting the sealing member. The two flanges are then axially clamped by screws and nuts in order to guarantee leaktightness around the solid disc. In order to pass the lance through the pipe, the two flanges are unclamped and the disc provided with the through opening for the lance is pivoted into the axial position between the two flanges, before reclamping the flanges axially. The axial sealing member of this device is fitted with a simple packing box. In order to compensate for a slight axial misalignment of the lance, the axial sealing member is fixed onto the second flange so as to be movable perpendicularly to the central axis of the device. For various reasons such as productivity and other reasons it is self-evident that a device of this type has not been and is not currently satisfactory. In fact, during the exchange of the solid disc and the pierced disc, the device provided is even incapable of avoiding leaks from the pressurized container.
An improved embodiment of this device is known from German Patent Application DE 15 33 829. The closure member also comprises a double disc with a through opening for the lance. This double disc is, however, surrounded by a leaktight casing, in which it is pivotable about a pivot axis parallel to the central axis of the device and has a slight axial clearance on this pivot axis. In order to improve the leaktightness around the solid disc, and the pierced disc respectively, the device is fitted with an annular hydraulic piston which is equipped with sealing gaskets. When this annular hydraulic piston is actuated, these sealing gaskets are applied onto the respective disc which is in front of them. This disc in turn bears on sealing gaskets integrated in an axially opposite surface. A disadvantage of this solution is that, during the pivoting of the double disc, the sealing gaskets bearing on the double disc are highly stressed. In order to increase the life of the sealing gaskets the aforementioned patent application provided these sealing gaskets with a special lubricating system. It will also be noted that, in the event of sealing problems with the annular hydraulic piston, the leaktightness of the device provided in this German Patent can no longer be reestablished.
It will be appreciated that there is a need to provide a device equipping an opening made in a pressurized container, in particular a blast furnace, for the axial insertion of a lance therein, which ensures more reliable leaktightness than the devices of the prior art.